St. Tammany farmer. [volume] (Covington, La.) 1874-current, 1887-10-01
ABOUT LIGHTNING.


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Every one is familiar With The fact
mat lightning does not spring direct
trom cloud TO clood, or to the earth. hut
pnrsues . sigzag course. This il due to
No TACT that the air is not equally humid
throughout Electricity always takes
me path which offers the least resistance
1oits passage. Damp air is . much bet.
Ter conducting medium than dry air
consequently the lightning selects tho
lamp route. avoiding the drier strata
ana zones its encounters. and advances.
now directly. now obliquely, until it
reaches the opposite cloud, where it sub.
1ivides into number OF forks. Owing
20 the resistance which it encounters in
uspath. intense heats generated. which
causes the air to expand. Immediately
after the fash. the air again contracts
with great violence and With loud re-
port which is echoed and re-echoed
among the clouds. The report reaching
the ear OF the listener from varying dis
tances. is drawn out into a series, and.
being still further prolonged by tho
echoes. the roll of thunder is produced.
1t Is . curious fact that, although tho
sound Of thunder is exceedingly loud
when heard near at hand. the area over
which it is audible is comparatively cir
cumscribed. The noise Of cannonaeie
will be heard, under favorable condi-
tons. at . distance Of nearly one hum
dred miles. while the sound of thunder
hoes not travel over fifteen miles. TIE
occurrence of the thunder and lightning
Is. OF course. simultaneously: but as tho
light travels faster than sound-its pas
sage is practically instantaneous-the
Hash may be seen several seconds before
the thunder is heard. The distance of
thunder may thus Be approximately
estimated, an interval of five seconds
between the fash and the thunder-clap
being allowed to each mile.
Sheet lightning has the appearance
OF sheet Of fame momentarily illnmi-
mating part Of the sky or cloud surface.
1t is. in reality. but the reflection of
lightning flashing beyond the horizon
or behind the clouds. and at too great .
distance for the thunder to be audible.
But the most remarkable of all man
ifestations Of electricity is globular
lightning. in appearance like ball Of
fire moving lcisrrely along. and re-
naming visible. it may be. several min.
utes. Many curious accounts are re.
lated Of its vagarics. One Of the most
interesting and circumstantial is that
given by Mr.. Fitzgerald, County
Donegal Ireland, who saw globe Of
fire slowly decend from the Glendowan
mountains to the valleys below. When
it first touched the ground. it excavated
hole about twenty feet square. las il
had been cut out with = huge knife"
This was scarcely the work of a minute.
For a distance of twenty perches it
plowed a trench about four feet deep.
and. moving along the bank of a stream.
it made . furrow . foot in depth.
Finally. it tore away part Of the bank
five perches in length and five feet
deep, and ''hurling the immense mass
into the bed Of the stream it flew to the
opposite peaty bank" The globe was
visible twenty minutes and traversed .
distance Of a mile. showing that its pro-
gress was, for lightning. very slow in
deed. During thunder storms of ex-
trcme violence on Decside. balls of fire
are occasionally seen to roll down tho
sides of Lochnagar, which are no doubt
identical with globular lightning
Chambers Journal.